A274591 - OEIS

%I #19 Jun 05 2018 03:15:40

%S 73,22049,90707201,4359889

%N Least number k such that k-1, k, k+1 are the sum of two nonzero squares in exactly n ways.

%C Corresponding triples are (72, 73, 74), (22048, 22049, 22050), (90707200, 90707201, 90707202), (4359888, 4359889, 4359890) for first four terms.

%C a(6) = 1428907401, a(8) = 2305281745. No more terms < 2*10^11. - _Lars Blomberg_, Jun 01 2018

%C a(5) > 10^15, if it exists. - _Giovanni Resta_, Jun 05 2018

%e a(2) = 22049 because 22048 = 12^2 + 148^2 = 68^2 + 132^2, 22049 = 32^2 + 145^2 = 40^2 + 143^2, 22050 = 21^2 + 147^2 = 105^2 + 105^2.

%Y Cf. A064716, A274548.

%K nonn,hard,more

%O 1,1

%A _Altug Alkan_, Jun 29 2016